The four-year anniversary of a painful night in the career of Kevin Garnett arrives next Tuesday.

On Feb. 19, 2009, in the second quarter of a road game against the Utah Jazz, Garnett went up to grab an alley-oop pass from Paul Pierce and suffered a right knee injury.

He would play only four more regular-season games in late March for the Celtics and missed the playoffs before undergoing the first surgery of his career in May.

When Garnett returned for training camp in the fall of ’09, he was a 33-year-old player with a lot of basketball miles on his odometer coming off an injury that had been more extensive than initially thought.

Was that night four years ago in Salt Lake City going to mark the beginning of the decline of Garnett’s effectiveness? Would the intensity that had burned so deep he entered the NBA the mid-1990s start to cool off?

At the age of 36, with 1,307 regular-season games and 47,353 minutes on his resume, Garnett is still going strong, leading the Celtics in rebounds (7.7 per game) and is second to Paul Pierce in scoring (15.1 points on 50 percent shooting).

In the history of the Celtics, only two players have averaged 15 or more points after turning 36 years old – John Havlicek and Robert Parish.

The years may have made Garnett a step slower, but he continues to be a productive player with his 37th birthday approaching on May 19.

“At this stage of my career,’’ said Garnett, “I’m fortunate to be out here and be healthy and play the game that I love.’’

On Sunday night, Garnett will again be suiting up with the game’s elite in the annual NBA All-Star Game in Houston. Garnett has been selected to play in the game 15 times during his 18 seasons in the league.

That knee injury in ’09 threw a scare into him since it marked the first time Garnett had been through anything like that.

In the four seasons since returning from surgery, Garnett’s playing time has been closely monitored by Celtics coach Doc Rivers, but he has continued to play at a high level.

Page 2 of 2 - He remains constantly in motion on the court, directing traffic at the defensive end and playing a versatile offensive game.

“The energy that I have is something I’ve never paid attention to,’’ said Garnett. “I just know I have it. I think you go at the game 100 percent, nothing less than that.

“If you can go higher than 100 percent, then so be it. For the most part, while you’re out there, play hard.’’

Garnett, who recently scored his 25,000th point, has been as advertised since joining the Celtics in the summer of 2007. He changed the approach of the team with his unselfish play and intensity from Day One.

“He’s a great person, great guy in the locker room, the most unselfish superstar I’ve ever been around,’’ said Rivers. “I don’t know if there’s other guys – maybe Ray Lewis comes to mind in football. But it’s all about his team. He literally loves his team and he literally does not like the other team. I like it.’’

Garnett signed a three-year contract last summer, meaning he would be playing until the age of 38 if the deal is fulfilled. But after Wednesday night’s win over the Chicago Bulls, Garnett told reporters, “This is definitely my last all-star game.”

Was that a hint that Garnett might retire after this season? Garnett, reminded he has two years left after this one and could be back at the all-star game in the future, said, “Y’all don’t know what I know.’’

In Houston on Friday, though, Garnett downplayed the notion he would retire after this season.

Whenever the final game of Garnett’s career with the Celtics is played, though, it is safe to say he will play it the same way as always – full of intensity and unselfishness.